The present invention relates generally to the field of semiconductor processing equipment. More particularly, the present invention relates to a method and apparatus for dispensing fluids onto a semiconductor substrate. Merely by way of example, the method and apparatus has been applied to two processing stations in a single chamber in a coat/develop module. However, it would be recognized that the invention has a much broader range of applicability.
Portions of the process of forming electronic devices are commonly performed in a multi-chamber processing system (e.g., a cluster tool) that has the capability to sequentially process substrates, (e.g., semiconductor wafers) in a controlled processing environment. A typical cluster tool used to deposit (i.e., coat) and develop a photoresist material, commonly known as a track lithography tool, will include a mainframe that houses multiple substrate transfer robots which transport substrates between a pod/cassette mounting device and multiple processing chambers that are connected to the mainframe. Cluster tools are often used so that substrates can be processed in a repeatable way in a controlled processing environment. A controlled processing environment has many benefits, which include minimizing contamination of the substrate surfaces during transfer and during completion of the various substrate processing steps. Processing in a controlled environment thus reduces the number of generated defects and improves device yield.
Two types of processing chamber generally included in a track lithography tool are substrate coating modules and substrate developing modules, sometimes collectively referred to as a coat/develop module. Typically, in a coat module, a spin coating process is used to form a layer of photoresist or other coating on an upper surface of a substrate. One method mounts a substrate on a spin chuck, which is rotated at up to several thousand revolutions per minute (RPM). Several milliliters of a liquid (e.g., photoresist) is applied to a central region of the substrate and the spinning action of the spin chuck disperses the liquid over the surface of the substrate. The coating is processed in subsequent steps to form features on the substrate as is well known to one of skill in the art. In develop modules; a developer is applied to the surface of the substrate after exposure of the photoresist. The coat/develop modules contain a number of similarities, as well as differences, including different nozzle designs corresponding to varying viscosities of dispense fluids, among other factors.
In some previously known coat/develop modules, a single spin bowl is attached to a system for dispensing photoresist or other coating liquids. In some photoresist coating applications, it is desirable to provide a number of different coatings, including different thicknesses and materials. Particularly, the industry transition to 300 mm substrates has led to an increase in the number of different coating liquids. Accordingly, in some coat/develop modules, and particularly in photoresist coat modules, the dispense system may include a number of different dispense nozzles dispensing different photoresists. Additionally, a number of other dispense nozzles may be included that provide photoresists with varying concentrations of solutions and solvents.
In some coat/develop modules, the dispense nozzles are fabricated to precise tolerances in accordance with the tolerances associated with a particular semiconductor process. As a result of the number and quality of the dispense nozzles in some of these modules, the cost of the dispense system may be much larger than the cost of the spin bowl.
In general, coat/develop applications rotate the substrate to achieve a predetermined rotation speed, dispense the coating fluid, and then continue rotating the substrate for a predetermined period after the dispense step is completed. As described above, the rotation of the substrate is utilized to disperse the coating/developing fluid over the surface of the substrate. In these processes, the dispense system is inactive while the substrate rotation dispenses the resist. Therefore, in some dispense systems, the most expensive system components, namely those included in the dispense apparatus, are idle during a significant fraction of the processing time.
As the complexity of the devices fabricated increases, so does the need for more accurate and efficient processing equipment. Traditionally, the throughput (# of substrates processed/hour) of a developer system was limited by the number of develop chambers present in the system. The demand for lower Cost of Ownership (CoO) is increasing with each successive generation of semiconductor equipment. One of the important factors in calculation of the CoO is the throughput of the system. The throughput of a system is inversely proportional to its CoO. To satisfy the requirements for lower CoO, a higher throughput for the system is desirable. Thus, there is a need in the industry to deploy substrate-processing systems that can process more wafers per hour but do so with an existing or lower footprint. This will ensure that advantages gained by the increase in throughput are not offset by a larger footprint of the system and consequently lead to a lower footprint productivity.
Therefore, a need exists in the art for improved coat/develop modules and improved methods of operating the same.